Validations of BIA

The following abstracts validate the use of BIA for estimating body composition, either in general populations or for a specific subset.

Journal of the American Dietetic Association. 2007 Aug;107(8):A29

Validation of Bioelectrical Impedance Against Dual-Energy X-Ray Absorptiometry in Adult, African American Females.

M.W. Valliant, D.K. Tidwell

The assessment of body composition (BC), specifically fat mass and fat-free mass is an important component of establishing nutritional status. Bioelectrical impedance (BIA) is a commonly used, non-invasive, low cost method to measure BC. African American (AA) females have a high rate of obesity so knowledge of BC is important to professionals working with this population. The objective of this study was to compare BIA (hand to foot model) to dual-energy X-ray absorptiometry (DXA) as the reference. BC was assessed by BIA (BIA 101 RJL System) and DXA (Hologic Delphi-W) in 100 healthy, AA females 18 – 40 years old with various body mass indices (range 17 – 47 kg/m2; mean = 29.53 +/- 6.86 s.d.). Both measures were completed in the morning following an overnight fast, physical inactivity for the previous 24 hours and in the supine position. Pearson.s correlation coefficient 0.94 (p = .01) indicated a strong correlation between the two methods and no significant statistical difference between the means (p = .72). Bland and Altman analysis showed strong agreement between the two methods across the range of body fat percentages indicating that they are comparable methods for measuring body fat percentage at lower and higher percentages of body fat. In conclusion, BIA is a suitable method to assess BC in adult AA females when factors such as food and beverage intake and physical activity are controlled.

Department of Nutritional Sciences, The University of Arizona, Tucson, AZ.

AIM: Equations for estimating % fat mass (%BF) and fat-free mass (FFM) from bioelectrical impedance analysis (BIA) that work in adolescent girls from different racial/ethnic backgrounds are not available. We investigated whether race/ethnicity influences estimation of body composition in adolescent girls. PRINCIPAL PROCEDURES: Prediction equations were developed for estimating FFM and %BF from BIA in 166 girls, 10-15 years old, consisting of 51 Black (B), 45 non-Black Hispanic (H), 55 non-Hispanic White (W) and 15 mixed (M) race/ethnicity girls, using dual energy x-ray absorptiometry (DXA) as the criterion method. FINDINGS: Black girls had similar %BF compared to other groups, yet were heavier per unit of height according to body mass index (BMI: kg.m(-2)) due to significantly greater FFM. BIA resistance index, age, weight and race/ethnicity were all significant predictors of FFM (R(2) = 0.92, SEE = 1.81 kg). Standardized regression coefficients showed resistance index (0.63) and weight (0.34) were the most important predictors of FFM. Errors in %BF (~2%) and FFM (~1.0 kg) were greater when race/ethnicity was not included in the equation, particularly in Black girls. We conclude the BIA-composition relationship in adolescent girls is influenced by race, and consequently have developed new BIA equations for adolescent girls for predicting FFM and %BF.

OBJECTIVE: To compare the accuracy of percentage body fat (%BF) estimates between bioelectrical impedance analysis (BIA) and DXA in obese African-American women. RESEARCH METHODS AND PROCEDURES: Fifty-five obese African-American women (mean age, 45 years; mean BMI, 38; mean %BF, 48%) were studied. BF was assessed by both BIA (RJL Systems BIA 101Q; RJL Systems, Clinton Township, MI) and DXA (Hologic QDR-2000 Bone Densitometer; Hologic Inc., Bedford, MA). Generalized and ethnicity- and obese-specific equations were used to calculate %BF from the BIA. Bland-Altman analyses were used to compare the agreement between the BIA and the DXA, with the DXA serving as the criterion measure. RESULTS: Two of the generalized equations provided consistent estimates across the weight range in comparison with the DXA estimates, whereas most of the other equations increasingly underestimated %BF as BF increased. One of the generalized and one of the ethnicity-specific equations had mean differences that were not significantly different from the DXA value. DISCUSSION: The findings show that the Lukaski equation provided the most precise and accurate estimates of %BF in comparison with the QDR 2000 and provide preliminary support for the use of this equation for obese African-American women.

BACKGROUND: Interest in the study of body composition in childhood is increasing. Bioelectrical impedance analysis (BIA) is an accurate and reliable method. OBJECTIVES: To determine anthropometric parameters, fat-free body mass and fat body mass using BIA and anthropometry, and to establish their relationship. MATERIAL AND METHOD: A total of 365 healthy children (188 boys, 177 girls) aged 6.0 to 14.9 years were studied. Weight, height, arm circumference, skinfolds (bicipital, tricipital, subscapular and suprailiac) and bioelectrical parameters were measured. Body density was calculated from the four skinfold measurements using Brook’s formula. Bioelectrical impedance was measured with a BIA-101 S (RJL Systems) using a fixed frequency (50 kHz). Fat-free body mass from BIA was calculated using Deurenberg’s equation (FFM = 0.82 x height2/resistance). RESULTS: We present the mean, standard deviation and 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th and 97th percentiles of anthropometric variables and fat mass and fat-free mass estimated using BIA. Correlations were found between fat-free mass estimated using BIA and anthropometric variables. The reliability of BIA in estimating fat mass was assessed with intraclass correlation coefficients, which were excellent (0.948 in boys, and 0.945 in girls). CONCLUSIONS: BIA is an easy, low-cost, and highly reliable method, making it a useful technique for studying human body composition. This method shows excellent correlation with anthropometric variables.

Body composition methods were examined in 20 women [body mass index (BMI) 48.7 +/- 8.8 kg/m(2)] before and after weight loss [-44.8 +/- 14.6 (SD) kg] after gastric bypass (GBP) surgery. The reference method, a three-compartment (3C) model using body density by air displacement plethysmography and total body water (TBW) by H(2)18O dilution (3C-H(2)18O), showed a decrease in percent body fat (%BF) from 51.4 to 34.6%. Fat-free mass hydration was significantly higher than the reference value (0.738) in extreme obesity (0.756; P < 0.001) but not after weight reduction (0.747; P = 0.16). %BF by H(2)18O dilution and air displacement plethysmography differed significantly from %BF by 3C-H(2)18O in extreme obesity (P < 0.05) and 3C models using (2)H(2)O or bioelectrical impedance analysis (BIA) to determine TBW improved mean %BF estimates over most other methods at both time points. BIA results varied with the equation used, but BIA better predicted %BF than did BMI at both time points. All methods except BIA using the Segal equation were comparable to the reference method for determining changes over time. A simple 3C model utilizing air displacement plethysmography and BIA is useful for clinical evaluation in this population.

BACKGROUND: Amyotrophic lateral sclerosis (ALS) is a neurologic disease with an unfavorable prognosis that may be accompanied by malnutrition or overweight. Nutritional status is difficult to evaluate in these patients because of their physical limitations and the asymmetry of their disease involvement. Bioelectrical impedance analysis (BIA), which enables bedside analysis of body compartments, has not been adequately validated for use in patients with ALS. OBJECTIVE: We compared reference measures of fat-free mass (FFM(a)), obtained by dual-energy X-ray absorptiometry, with FFM obtained by BIA and by the skinfold-thickness technique. DESIGN: We measured FFM(a) in 32 ALS patients. Anthropometric measures included weight, height, skinfold thickness, and arm and wrist circumferences. The fat mass obtained from the skinfold-thickness measures enabled us to calculate FFM. BIA was performed by measuring the bioimpedances at 5, 50, and 100 kHz of each side of the body and from one side to the other. FFM was calculated by using the instrument’s internal software and by using 3 standard equations. The concordance between the methods was evaluated by the Bland-Altman test. RESULTS: Two of the 16 measured FFM values were not significantly different from FFM(a). However, the risk of dispersion was too high to be acceptable in practice. An equation was then developed by using multivariate analysis, with impedance at 50 kHz. This equation was validated in a second population of 15 ALS patients and with the use of 2 successive measurements performed on 18 patients. CONCLUSION: BIA is a simple technique that is valid for use in ALS patients, both for a single exam measure and for longitudinal monitoring, with the use of an adapted equation and a frequency of 50 kHz.

Phys Ther. 1993 May;73(5):320-8.

Cross-validation of bioelectrical impedance analysis of body composition in children and adolescents.

Wu YT, Nielsen DH, Cassady SL, Cook JS, Janz KF, Hansen JR.

Physical Therapy Graduate Program, University of Iowa, Iowa City 52242.

BACKGROUND AND PURPOSE. The reliability and validity of measurements obtained with two bioelectrical impedance analyzers (BIAs), an RJL Systems model BIA-103 and a Berkeley Medical Research BMR-2000, were investigated using the manufacturers’ prediction equations for the assessment of fat-free mass (FFM) (in kilograms) in children and adolescents. SUBJECTS. Forty-seven healthy children and adolescents (23 male, 24 female), ranging in age from 8 to 20 years (mean = 12.1, SD = 2.3), participated. METHODS. In the context of a repeated-measures design, the data were analyzed according to gender and maturation (Tanner staging). Hydrostatic weighing (HYDRO) and Lohman’s Siri age-adjusted body density prediction equation served as the criteria for validating the BIA-obtained measurements. RESULTS. High intraclass correlation coefficients (ICC > or = .987) demonstrated good test-retest (between-week) measurement reliability for HYDRO and both BIA methods. Between-method (HYDRO versus BIA) correlation coefficients were high for both boys and girls (r > or = .97). The standard errors of estimate (SEEs) for FFM were slightly larger for boys than for girls and were consistently smaller for the RJL system than for the BMR system (RJL SEE = 1.8 kg for boys, 1.3 kg for girls; BMR SEE = 2.4 kg for boys, 1.9 kg for girls). The coefficients of determination were high for both BIA methods (r2 > or = .929). Total prediction errors (TEs) for FFM showed similar between-method trends (RJL TE = 2.1 kg for boys, 1.5 kg for girls; BMR TE = 4.4 kg for boys, 1.9 kg for girls). DISCUSSION AND CONCLUSION. This study demonstrated that the RJL BIA with the manufacturer’s prediction equations can be used to reliably and accurately assess FFM in 8- to 20-year-old children and adolescents. The prediction of FFM by the BMR system was acceptable for girls, but significant overprediction of FFM for boys was noted.

Division of Pediatric Cardiology, Mount Sinai School of Medicine, New York, NY 10029.

This study validated further the bioelectrical impedance analysis (BIA) method for body composition estimation. At four laboratories densitometrically-determined lean body mass (LBMd) was compared with BIA in 1567 adults (1069 men, 498 women) aged 17-62 y and with 3-56% body fat. Equations for predicting LBMd from resistance measured by BIA, height, weight, and age were obtained for the men and women. Application of each equation to the data from the other labs yielded small reductions in R values and small increases in SEEs. Some regression coefficients differed among labs but these differences were eliminated after adjustment for differences among labs in the subjects’ body fatness. All data were pooled to derive fatness-specific equations for predicting LBMd: the resulting R values ranged from 0.907 to 0.952 with SEEs of 1.97-3.03 kg. These results confirm the validity of BIA and indicate that the precision of predicting LBM from impedance can be enhanced by sex- and fatness-specific equations.

This study was conducted to validate the relationship between bioelectrical conductance (ht2/R) and densitometrically determined fat-free mass, and to compare the prediction errors of body fatness derived from the tetrapolar impedance method and skinfold thicknesses, relative to hydrodensitometry. One-hundred and fourteen male and female subjects, aged 18-50 yr, with a wide range of fat-free mass (34-96 kg) and percent body fat (4-41%), participated. For males, densitometrically determined fat-free mass was correlated highly (r = 0.979), with fat-free mass predicted from tetrapolar conductance measures using an equation developed for males in a previous study. For females, the correlation between measured fat-free mass and values predicted from the combined (previous and present male data) equation for men also was strong (r = 0.954). The regression coefficients in the male and female regression equations were not significantly different. Relative to hydrodensitometry, the impedance method had a lower predictive error or standard error of the estimates of estimating body fatness than did a standard anthropometric technique (2.7 vs. 3.9%). Therefore this study establishes the validity and reliability of the tetrapolar impedance method for use in assessment of body composition in healthy humans.

These papers and abstracts of papers have been published in peer-reviewed journals. They may draw conclusions and discuss applications of Bioelectrical Impedance Analysis which have not been reviewed by the FDA. Statements made within them are the sole responsibility of the authors. Unless otherwise indicated, no material support was provided to the authors or study investigators by RJL Systems.